ruvA and ruvB mutants specifically impaired for  replication fork reversal.
Replication fork reversal (RFR) is a reaction that takes place in Escherichia coli at replication forks arrested by the inactivation of a replication protein. Fork reversal involves the annealing of the leading and lagging strand ends; it results in the formation of a Holliday junction adjacent to DNA double-strand end, both of which are processed by recombination enzymes. In several replication mutants, replication fork reversal is catalysed by the RuvAB complex, originally characterized for its role in the last steps of homologous recombination, branch migration and resolution of Holliday junctions. We present here the isolation and characterization of ruvA and ruvB single mutants that are impaired for RFR at forks arrested by the inactivation of polymerase III, while they remain capable of homologous recombination. The positions of the mutations in the proteins and the genetic properties of the mutants suggest that the mutations affect DNA binding, RuvA-RuvB interaction and/or RuvB-helicase activity. These results show that a partial RuvA or RuvB defect affects primarily RFR, implying that RFR is a more demanding reaction than Holliday junction resolution.
Le Masson
Marie
M
CNRS, Centre de Génétique Moléculaire, UPR 2167, Gif-sur-Yvette, F-91198, France.
Baharoglu
Zeynep
Z
Michel
Bénédicte
B
D000595:Amino Acid Sequence; D019943:Amino Acid Substitution / Q000235:genetics; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism*; D004265:DNA Helicases / Q000235:genetics* / Q000378:metabolism*; D004261:DNA Replication; D004269:DNA, Bacterial / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics / Q000502:physiology*; D029968:Escherichia coli Proteins / Q000235:genetics* / Q000378:metabolism*; D050296:Microbial Viability; D008954:Models, Biological; D008958:Models, Molecular; D008969:Molecular Sequence Data; D020125:Mutation, Missense; D011485:Protein Binding; D011995:Recombination, Genetic
D001426:Bacterial Proteins; D004269:DNA, Bacterial; D029968:Escherichia coli Proteins; C061260:RuvB protein, Bacteria; C071059:Holliday junction DNA helicase, E coli; D004265:DNA Helicases